Climate Change/Evidence of Change

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By using various methods of chemistry, geology, and even astronomy, past climate variations are well known. These include the relatively periodic ice ages of the past 2-million years as well as more exotic climates from the Cretaceous and other eras. On such long timescales the main reasons for climate changes must be linked to changes in the sunlight reaching Earth (insolation), major shifts in ocean heat transport, or "external" forcing like volcanism or meteor impacts. More recently, human-induced changes (anthropogenic) are likely a strong climate forcing. Much research has focused on quantifying Earth's climate and its variability over the past 30 years or more. It has been shown that the globally averaged surface temperature is now warmer than it has been for at least 150 years. The trend in surface temperature is remarkably well correlated with a trend in atmospheric carbon dioxide. The current trends are increasing, and the warmest years on record are in the last decade. IPCC

Indeed, over the past century or so the global (land and sea) temperature has increased by approximately 0.6 ± 0.2°C

Earth is now absorbing 0.85±0.15 W m^-2 more energy from the Sun than it is emitting to space. (Hansen et al, 2005, Science vol 308)

Some of the observed evidence that Earth's climate is changing:

• Global Temperatures are Rising
• Melting Glaciers
• Sea Levels Rising